1. Field of the Invention
The present invention relates to communication for the installation of large-volume content into non-broadband communication devices such as mobile telephones and personal digital assistants (PDAs).
2. Description of the Related Art
Conventionally, installation and authentication pose a problem for large-volume dictionaries and e-learning content of mobile devices such as mobile telephones and PDAs. Conventional authentication technology includes an established scheme, described below, for encrypting content by using information unique to a device as a key. However, as dictionaries such as Kojien have a large volume of 130 MB (main bodies and index), the scheme cannot be put into practical use.
Establishment of a technology to indirectly use personal computers (PCs) for the authentication and installation of dictionary content to mini-SD cards or hard discs (HDs) of mobile telephones, PDAs, etc. via compact disc read-only memory (CD-ROM) or broadband communication is necessary.
Conventional installation/authentication schemes include, for example, a scheme disclosed in Japanese Patent Application Laid-Open Publication No. 2002-099832, whereby a content distribution server adds copy protection information using the mobile telephone number of a request source as a key to allow only the request-source mobile telephone to use the content.
However, with such schemes, a problem arises in that the content becomes unusable if the mobile telephone is switched to another mobile telephone. Consequently, Japanese Patent Application Laid-Open Publication No. 2004-048540 discloses a scheme where content is encrypted using information unique to the terminal apparatus requesting the content as a key such that the content cannot be decrypted in other terminals.
Meanwhile, although small to medium-size dictionary content may be downloaded and sold according to some schemes, problems arise in terms of capacity, time, communication costs, and authentication. Such downloading (installation) schemes include two types, a full-downloading scheme and a server-and-browser scheme.
The full-downloading scheme is a scheme of downloading (installing) all the content files, block data, and a program for retrieving/reproducing the data in a client system. On the other hand, the server-and-browser scheme is a scheme of using a client browser to retrieve/reproduce data in a server without downloading (installing) the data such as files.
The conventional technology disclosed in Japanese Patent Application Laid-Open Publication No. 2004-048540 is highly effective in preventing unauthorized use since no unique information is added to content and hence, the content is encrypted in its entirety. However, as the text and index data of the fifth edition of Kojien has a volume of approximately 130 MB, the technology is impractical for such large-volume dictionary content with respect to mobile telephones, as described below.
It takes a few hours or more to download the large-capacity dictionary content through non-broadband (narrowband), which poses a problem of practicality. Such download may incur high packet charges of few thousand yen or more, or for some content, several hundred thousand yen, further posing a problem of practicality.
Schemes enabling the download (installation) and sale of small to medium-size dictionary content (the full-downloading mode and the server-and-browser mode) require a large amount of download (install) time for large-volume dictionary content, posing a problem of practicality. Such download may incur high packet charges such of a few thousand yen or more, or for some content, several hundred thousand yen, again posing a problem of practicality. Further, as mobile telephones need a large capacity storage medium under such schemes, a problem of increased mobile telephone cost arises.